Synthesis and characterisation of Copper based bulk amorphous/nanophase alloys as melt spun ribbons

Abstract

Zr-based bulk metallic glass alloys were known to have good glass forming ability (GFA) and better mechanical properties but these are very costly and have difficul-ties in processing. On the other hand, recent reports on Cu-based metallic glass show even better mechanical proper-ties and good GFA. Cu-based BMG's may emerge as a high strength and futuristic engineering materials. Therefore, in this project, a few copper based alloy ribbons with nominal composition Cu60ZrxTi40-x (x=0,10,20,30,40) were prepared by AR-arc melting followed by melt spinning to produce amorphous ribbons. XRD and TEM studies revealed the amorphous nature of the as cast ribbons. DSC scans indicated exothermic peaks corresponding to different cystallizations. It is observed that, (1)the glass trans-ition temperature and crystallization temperature increase (2) the mode of crystallization changes from single to multiple stages, with the addition of zirconium. The activ-ation energies of the transformation were determined by kissinger's peak shift method. Super cooled liquid region (^Tx=Tx-Tg) has a bearing on the Zr content. Reduced glass transition temperature Trg(=Tg/Tl) of Zr containing alloys was found -0.6, a criteria for bulk metallic glass forma-tion. The maximum ultimate tensile strength (UTS) obtained for these alloy ribbons were -1700Mpa. Results of these studies indicate that a few of these alloy compositions can be casted as bulk rods of high strength in Cu-mold. Thus this work can be extended to produce copper based bulk metallic glass rods of high strength.